Automatic trunking system.



P. J. 'TRUBY. MAQ TOMATIG TRUNKING SYSTEM. APPLIog'r'IoN FILED JAN. 1a, 1911.

Patented 1Jec.29,1914.` i

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P. J. TRUBY.

AUTOMATIC TRUNKING SYSTEM.

y APPLICATION HLBD JAN. 1a. 1911.

,Patented 1390.29, 191.4l

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F. J'. TRUBY.

AUTOMATIC TRUNKING SYSTEM.

APPLIOAYION FILED JAN. 1B, 1911A Patented Dec.,` l29, 1914.

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Y MiN/ #754555 UNrrED sTA'rn-sgrmvr OFFICE.;

FRANKLIN J. TRUBY, 0F CHICAGO, ILLINOIS, ASSIGNOR TO AUTO-MTIC ELECTRIC 4 COMPANY, 0F CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TRUN'KING SYSTEM.

Specication of Letters Patent.

` Application led January 1 8, 191.1'. Serial No. (503,5),03.v i

. To all whom it may concern Be it known that I, FRANKLIN J. Tamar, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvement in Automatic TrunkinglSys tems, o'fjwh-ichf the following is a specification,l Y' p.

My invention relates to telephone exchangesysltems in general, but more'partlcularly to. systems in which automatic trunk'- ing, switches are -employed,fand especially Vto systems. in which;A a nonnum'erical trunkf ing switch is allotted lto' each subscrlbers telephone line..V Previous .to my invention these 'trunkin'g switches, such as the v'said subscribers-line switches, have been operated in various"ways.` 'For example, these switches have been lctlmstructed to operate on the' rotaryfprinciplm and provided: with p means whereby th'ey. are always restored to normal'position or starting point after each call'. 'Inf other cases these switches have been'so' constructed and voperated that the trunk lines are selected ahead of the calls,

' each switch, while at rest, being in selective Amay be selected for the next callin scrlberz In other words. and with this second method, each calling 'subscriber not' relation to some other line.

relation tothe next idletrunk line, so that -the irst calling subscriber will get the preselected trunk line. The irstmethod has been found to be' objectionable` for various reasons, as, for' example, if several trunks are busy it requires some time for the line switch vof the calling linev to find an idle trunk, and during this operation the calling subscriber mayr begin calling the number of" the called subscriber by transmitting electrical impulses in the usual and well known Y way, in which event the call would not go through in the proper manner.4 The second.. method has also been found to be more orfless objectionable, in my judgment,'as each time a subscriber calls he causes the actu-a-v tion of all of the line switches of that] group'-that is to say, all the switches that are not in use-in order that another trunk .onlir causes the actuation of his own switch, 1n order to obtain connection with the prese- -lected trunk line, but also causes all of the idle line switches of that group to move off from sald line and-come to rest in selective .Y The object of mv invention is,tlierefore,

sub-

the provision of -an improved apparatus for I 'provide a trunking apparatus in which only one line switch operates when a'sub Patented Dee. 29, 1914.

scriber makes'a call--that is to say, only one i vin vthe group 4to 'which it belongs, and

which even this is often unnecessary, inasf-y much as each, switch is always `in electrical connection with the. trunk line which it last employed in extending the call, thereby.

making it possible forr a subscriber to-call again and get the same trunk line that he had for the previous call, `providing inthe interim the same has notbeen appropriated for use by some other subscriber,'it being imnecessary, when this is possible, for the -calling subscribers switch to rotate from* one trunk line to another in an effort to nd` one that is idle, as will hereinafter more;l fully appear.

In theaccompanying drawings, Figures 1 and 2 taken together represent a'complete vcircuit connection established between a call-jing substation A and a called'substation A@A ina system embodying the principles 'ofmyl" f invention.- Fig. 1 shows a substation Anto" thelline of which'there is allotted a so-called"- rotary line switch C. The line'- switch 4C I.

has access to a number of trli'iil lines, each4 of which leads to a selector 'similarr to the,

selector switchshown at D. Fig. 2 repre# sents diagrammatically a connector E, ro-

tary line switch C and@ substation AA: f The switch C- and substation'lAf fare similar 95 in -all respects to the, line switch'l C and substation A A offFig.'l 1. Y At'Ba battery is shown which is used for-'talking and oper# ating purposes. 'The'battery Bfhas its posi- Y, tive terminal preferably grounded at G At M a busy signaling' machine is repref sented and at Rl alf-ringing current generator' is'shown. 4 A V ,y Fig. 3 is a diagrammatic representation of the mechanism of the switch-ICJ Fig. 4 is a'modiied forrn" of':`the subscribv ers' individualv switch.

The substation's'wusedin a system embody-- a ing the principles'of gmy' invention maybe in connection with which l have elected to is also illustrate my invention comprise, at substation the receiver 2', switch hook 3, transmitter et, ringers il, condenser 6, irnpulse springs 7 and 8, which are forced out of engagement bythe teeth 9 on the impulse.-

2 and'impulse springs 7 and 8 are bridged across vthe line conductn's 15 and '16 in series,

' The j rotar-y 'line switch C comprises, among other details, the double-Wound revlay 17,' line relay 187 cutoff-relay 19 and the motor magnet with the interrupter I' set ofwipers '25 springs' 21.

22, 23 and 241 which, by means of the magnet'20, are rotated over banks of contacts 2 5, 26 and 27 which consist of terminals of 'trunk lines leading to selectors such asthe selector shown at D. The bank contacts of the various switches C are multiplied as shown in Fig. 1, thus making a number of trunk lines common to .a number of switches 1). The banks consist vof a number of individual segments a (Fig.

which form terminals of the trunks leading to the' selectors lil, and each also has a common 'segment which is connected to a. spring of the relays 1"( The Wipers are 'forjthe' purpose oi keeping one of the indi- 4-vidua'l contacts aiv 1n electrical connection with the common segment o. Each of the Wipers 22, 2 3 and 24 is provided with three arms, so that as one arm passes oil the last *contact another will pass onto the first one.

,Fig. '3, shows how the Wipers 22, 23 and 2li arerotated by the magnet 20 through the medium of the armature 9%, pawl 95, ratchet Wheel 96 and shaft 97.

Thaselector D is of the general type disclosed in United States Letters Patent No.

to rKeith,

815,321, granted March 13, 1906, Erickson end Erickson, being slightly modiied,'however,to operatein conjunction with atwowvire system-that is, a system in vwhich there is no ground connection used at the substation. The selector comprises the 'usual shaft (not shown) carrying the` wipers 28,29 and 30,- `which shaft has a vertical motion controlled, by the vertical magnet 31 and a rotary motion controlled by the rotaryrnagnet 32. The private vmagnet 33 operates the side-switch ycarrying timev imperi-i Se, 35, 136 and 37 in the usual and .Wellfknown manner, and

is. ,in turn; controlled. through" the Vme'` diuin of the y'sloyv-acting relay 3&3. The

the

The switch also comprises a scriber calls another.

tresses switch is also provided with the slowactlng relays 59 and 4&0, doublawound relay 11 and release magnet 42, The selector D has access to trunli; lines leading to connectors lsimilar to the connector .ll shown in Fig. 2.V

The connector shown at E is of the saine general type as that disclosed in 'United States Letters Patent lil 815,176, granted March 13, ,1906, -to l th, Erickson and.

Erickson. The connector, like' the vselector r D, is provided with the usual shftfcarrying the Wipers d3, it and 15, the vertical motion of which shaft is controlled by the vertical magnet d6, and thev rotary'moton by the rotary magnet if?. 1t also comprises the slow-actii'g relays t8 and 49, double-wound line relay 50, release magnet 51 and private magnet 52, which latter controls a side switch carrying the Wipers 53, 541, 5,5, 56 and 57,'and addition the connector is provided With a ringing 'relay 58, back-bridge relay 59 and the busy locking relay 60 clearer understanding of my improved sys em may be obtained from an explanationot the operation by which one sub- Assuming, for eX- ample, that the subscriber at substation A 'desires to call the subscriber at substation A', to which is allotted the line #220, the mode of operation is as follows: To call the number 220 the subscriber at sub-station A removes his receiver from the hook and operates his calling device once, in the wellknoufn manner, for each digit. The removal of' the receiver at the -substation A. closes an energizing circuit through the relay 18 of the switch C.' rlhis circuit eX- tend's from ground (r through the springs (31 and 62 oi2 the relay19, thence through thesprings and 64 of the relay .17 conductor 16, springs 12 and .14,iinpulse springs 7 and 8, receiif'er 2, transmitter 1, conductor 15, springs 65 and 66, relay 18, springs 67 and 68 to the battery lead 69, thence through battery B to ground G. The relay 18, upon energizing, closes -a circuit extending from ground G2 through thesprings 70 and 71, winding 753 of the relay 17, thence through the springs 67' and G8 to battery B. It the trunk upon which the Wipers 2 2,r23 and '2l are standing idle, the relay Will attract its armature, whereby the springs 64, 65 and 98 'are shifted out of engagement with the springs 63, 66 and 99 and into engagement with the springs 78, '79 and 100, respecn tively, and the spring 101 is shifted into engagement With the spring 102. lThe engage.- ment of the springs 64 and 65 With the springs 78 and 79 closes the line circuit to the selector E through the Wipers 22 and 24. 'The extending of the line conductors to the selector E closes an energizing circuit through. the vdoublenound line relay 41. This circuit extends :troni ground ,G3 through the lower Winding of the relay 4:1,

side-switch wiper 35, individual segment 7 6 of the bank 27, wiper 24, commonsegment 77, springs 78 and64, thence to and through the substationA, back over the conductor 15,through the springs and 79, common 4sf'egment of the bank 25, Wiper 22, individual I segment wiper 34 and upper winding of the relay 41 to the battery lead 69. The re frio flay 41, upon energizing, closes a circuit through `the slow relay '10, This circuit eX- tends from ground G4 through the springs relay40,A upon energizing, puts a guarding ground'potential on the .private bank contact of the trunks leading to the selector D inthe private banks of allofthe individual switches that have access to the selector D. Thus, as soon asthe relay 40 energizes there is (in this case) a ground potential o n the contacts 83, 84, etc. This guarding circuit extends from ground Gr5 through'the springs .81 and 82 and the relay et() to battery. The

85 and 86 and the conductor 87 to the said private bank contacts. The energiaing of thev relay 40 also disconnects the impulse spring S8 from the release magnet 42, and

connects the said impulse spring 8 8 through I the relay 88 tothe vertical magnet.

If thev trunk upon Which'the' wipers 22,

-i 23 and 24 are standing had een in use when 30.

the subscriber at substation A removed'the receiver, there vwould have been a guarding groundl potential on the privatebanl: contact, as described above,-Wlnch would have caused the wipers to have been advanced ofi this trunk to an idle `one. Upon the ener- 4gization of the relay 18 a circuit would have ..beenv closed .through the motor magnet 20 and Winding 89 of the relay 17. This circuit eXtends from the ground at the .pri-- vate bank contact through the wiper 23,

'common segment of the bank 26, conductor 90, springs 7 3. and 72 to the point 91, thence .one branch-leads through the winding 89 and springs 67 and 68 to battery. From the point 91 another branch extends through the interrupter springs 21, motor magnet 20, thence through the springs 67 and 68 to battery. The current in the winding89 opposes the current in the winding 7'5, thereby holding the relay 17 in a denergized posi tion, vin which position the trunk lines 92 and 93v are openat the springs 79- and-(8. The motor magnet 20, when its circuit is closed, attracts its armature 94. The `'pull-` ing up of the armatureQ-i breaks the circuit of its own magnet and also operates, through `vwhich immediately iallsvback.

23 finds another grounded Contact, causing the magnet 2() to again operate 1n a manner similar to that oi a buzzer to rotate the wipers past the busy trunk to an idle one.

(')it' course, as soon `as thecircuit of the winding SQiof the rela y 17 is broken by the Wiper 27% passing ott thelast guarded contact', the relay 17 is operated by the current in the winding 7 in the same manner as explained unen the wipers u'ere'resting on an idle Y The .shifting ofv the springs 64 and 65 *from engagement with the springs 63 and G6 and into cngagement'with the springs78 and 'T9' breaks the circuit oil the relay 1 8, The relay- 17' 'being-slightly slow acting holds up until tiiereiay l0. of the selectorl) pulls up, hereby ground potential' isplaccd on the spring 73 over a circuit hereinabove traced., As .the relay 18 d energizes', a holding cil'- cuit for the relay 17 is established, said circuit extending i'rom this ground potential vthrough the-.springs 73 and 74,sp1'ings 101 substation. The subscribcrat substation A now operates the calling device 'forthe first digit ot the desired number. The teeth 9 on thc impulse vvvheel 10 ope1'ate,du11ng the backward rotation ,of said impulse Wheel, tov

force the spring 8 outoi engagement with the spring 7. Whe-rch)Iv the circuitl through the relay 4.1 of the selector'D is4 broken twice.

The relay 4:1 denergizes to close a circuit through' the vertical ma griet 31 in serie-s with thev rela v 3S. from ground G4 through .the springs 81 and- This circuit extends 88, springs 103 and 161, slow relavi, vertical magnet 31 and side switch wiper 3G to battery.

The vertical lma gnet loperates tol raise the sha-ft and lsha :Ft Wipers two steps to the mediumgof lthe pawl 95 and ratchet wheel96 r(Figy to rotate the shaft 97' upon which are secured the Wipers 22, 23

and 24) one notch. As soonas the wipers I are moved onestepfthe wiperl 23 leaves the grounded contact. breaking the circuit. of

:the rotary magnet'20 and the Winding 89 of 1 vthe relay 17, if the. neit trunklis idle. If,

' however, the next trunk i s. `bi is y, the wiper apoint opposite the second level of -terminalsoftrunks leading to the 'connectorsll As soon as the vertical shaft is raised one or more steps the arm"111 allows the spring 112 to engage the'spring'll.-whereby one point in' the circuit of the release magnet 42 is closed. The relay T10 being slow`acting does-not .de'nergize duringthe momentary1 interruption of its energizing currentv b v the disengagement of the springs 81 and .82.

Also', the`v relay 88. which-'was energized when the first impulse vwas sent through it,-

.does not deiinergize. until a moment after the vio tact upon which it rests grounded in a man private magnet,

the side switch wipers to pass to second p05 s l last impulse has been transnntted.' ln' its' 38 closes an en-. ergizing circuit through the private magnet sition. The shifting of the wiper 36 from first to. second position shifts the battery connection iii-oni the vertical to the .rotary magnet. A circuit is now completed from 'ground G3 through the interruptor springs 108,-rotary magnet 32, slow relay 39 and side switch wiper 3G to battery. The rotary magnet energzes upon the closure of this circuit to rotate the shaft and 'wipers one step and onto the first contact of the second level, to press down the private 1nagnot armature and to break its own circuit at the intcrrlqiter springs. The armature l0?) `falls back when lthe circuit of itsmagnot is broken. It' the iirst contact is idle, the private armature will also fall back and '.iliow the side switch wipers to pass to third position. lf, however, the first contact is luisy, the private wiper will iindthe connerl which will be explained lz'tte1;, whereby' a circuit is closed' extending from said ground at the private bank Contact through the private wiper 29, conductor .110, side switch wiper 37 (in second position)- and private magnet 33 to battery. The private magnet encrgizos and holds its armature in an operated position, thereby locking the sido switch in the second position. The rotaf.'Y magnet airain cnergizes to rotate the shaft andv shaft wipers to the next bank Contact. v

lf the second trunk is idle, the side switch wipers will be allowed to pass to third position. lf, howeverl the second trunk is busy, the operations abovel described will be re peated to rotate 'thefwipcrs to the third contact, and so on until the Vprivate wiperv strikes the terminal ci a non-busy trunk, at which time the silo switch wipers will pass to the third position. The passing of the wipers 8i and to the third position cornpletes the line from 'the' calling; substation to the connector lil. thereby closing an ener owing circuit through the relay .50 of the said connector. This circuit extends from ground Ge through thelower winding1 of the relav 50 thence over the heavy conv duct-ors to and -through- 'thef substation fr and back ver the heavy conductors, and thririugh the upper winding of the relay 50 to battery. The relay 50, upon inatteso' energizing', closes the circuit of the re lay 49. This circuit extends from yground GT through the springs 114 and 115 and relay i9 to battery. 'The relay 49, upon energizing, shifts the spring 118 outof engage- 70 ment with the spring 117 and intoy engagement with the spring 119,.whereby the connection of the release magnet 51 with the impulse spring; 116 is broken, and the impulse spring 1 1@ is connected to Ical vmagnet 46. The engagement ofthe springs 121 and 122 puts a holding ground back on the slow relay 40 of the selector D, and also puts a guarding potential on the private bank contacts of the seized trunk in the banks of all of the selectors D that have access to the connector E. The latter circuit extends from ground GS through the side vswitch wiper 57, springs 122 and 1.21 and conductor 123 to the above-mentioned private g5 bank contacts. The former circuit extends over the same circuit to the private bank coutaet 121i, thence through'tlie private wiper 2). Aconductor 110, side switch wiper 37, springs 126 and 125 and -relay 40 to battery. short interval of time elapses,ho\veve1', between the time the side'switch-wipers of the iirst selector pass to the third position and the time that the above-mentioned Iguarding'potential is placed on the private bank g5 contacts. The relay 39 is supplied with a ground spring 127 for the purpose of placing a guarding;1 potential on the said private vbank contact until the ground is supplied from the connector. The relay 39, which im' Was energized in series with the rotary ma qnet, is slow acting; therefore ,it remains in` an energized .position for a moment after the side switch wipers have passed to the third position, whereby a ground is put on mi', the private bank contacts over a circuit extending from ground G9 through the springs 127 and 126, wiper 37,- conductor 110 and private wiper 29 to the said bank Contact.

0f course, it is evident that the relay 39 mi@ must be slightly 'quicker in its action than the release relay 40, otherwise "the switch would be released. i

The central office mechanism 'is nowfin readiness to respond to the operations ,cima

the calling device for the second digit 2.

As the subscriber at substatibn A operates.

the calling device for the-second digit 2, th'eline is again opened twice." The relay 500i the connectory denergizes twice to close va ma clrcuit through the vertical magnet 416 inf series with the relay 18, vthe same as described fer the selector D.v The vertical magnet operates-.to raise the shaft and shaft wipers two stepsto aposition oppositelthe 12.5,

second level of bank contacts. The .slow relay 48 denergizes a moment after the last impulse has been sentthrough, and permits the privat-e magnet 52 (which was energized over ar circuit extending from ground G10 the vertiposition.' The wiper 56, in passing to the second positioi, shifts the battery connec'.

tion from .the vertical to the rotary magnet. The subscriber at substation Anow operates the dial for the last digit O. `The line is opened ten times at the substation. The relay 50 denergizes ten times to close the circuit of the rotary magnet 47 ten times.

This circuit extends from ground G7 through the springs 114 and 116, 118 and 119,130 and 131, magnet 4 7, Wiper 56 and relay 48 to battery. The rotary magnet energizes and denergizes ten times to rotate the shaft and shaft wipers onto the contacts of the called line. The relay 48 does notdenergize until vthe last impulse has been transmitted. It .then denergizes and breaks the circuit of the private magnet 52, which in turn falls back and allows the `side switch wipers to pass to third position, The wipers 53 and 54, in passing to third position, ex-

tend theonductors from the calling line to the called substation A.' The wiper 55, in passing to third position, puts a guarding potentialbn the private bank contact .of the -called line in the banks of all of the con- 4nectors that have access to the called line.

This guarding potential extends from ground Gr11 through the side switch wiper 55, springs 168 and 169 to the private wiper 44, thence to the contacts above mentioned. A. circuit also extends Jfrom this ground at the private bank contact through the springs 132 and 133 and 'cutoff .relay 134 *to battery, The relay 134 energizes and disconnects both sides of the battery from the called line at the switch Cf, thus making it impossible for the subscriber at substation A' to call while. there is a connection on his line.` Then the wiper .57 asses from second to third position it shifts the holding ground for the release relay 40 of the se-- lector Dffrom ground G8 to ground Gr7 through the springsl 114 and 115. The wiper 56, .in passing to third position, disconnects battery from the rotary magnet and closes the circuit of the ringing relay 58. vThe .circuit through the relay 58 extends from 43. line conductor 140. bells 141, condenser 142. springs 143 and 144, line 145, wipers 45 and 53 and springs 146 and 147 to the other brush of the generator R. The interrupter andf153 and the' upper winding of the relay in the ringer relay circuit allows the bells to be rung intermittently. Upon hearing the -signal thesubscriber at substation A.

removes'the receiver from the hook, which thereupon, or-as soon thereafter as the ringer relayy denergizes, closes a circuit through the back-bridge relay 59, thus supplying the called i subscriber with talking battery current. This circuit extends from ground. G11 through the` lower winding of the relay ,59, springs 148 and 146, wipers 53 and 45, line 145, springs'144 and1149, impulse springs 150',v receiver 151, transmitter 152, Aline 140, Wipers 43 and 54, springs 139 B0 59 to battery. l The relay 59 energizes over this circuit and operatesto open the circuitv of. the ringer relay 58 at the springs 137 and 136. The subscribers atthe two'substations may now carry on an uninterrupted .g5 conversation until completed. The voice currents flow over' the heavy conductors shown in the drawings through the condensers 154 and 155. y l i The release of the central voffice mechanism is initiated by the hanging upv of the receiver at the calling substation. The l`re placing of the receiver on the hook at the calling substation opens the line by the'L disengagement of the springs 12 and 14'. 9155 The relay 50 of the connector E Afalls back when the line is thus opened, and opens the circuit of the relay 40 of the selector D and relay' 4 9 of the connector. The relay 49 falls "back, whereby. a circuit is closed through the release magnet 51.l This circuit extends from ground Gv through the springs 114 and 116, 118 and 117, magnet 51 and off normal springs 156 and 157 to batter-y. The

breaks the circuit of the releasemagnet.

The breaking of the holding cir uit of the relay 40 of the selector D allow-sitto de- 110 energize' and close the circuitfof the release magnet 42. This circuit` extends. from groundGt through the springs 81 and 88, springs 103 and i105-, o'fnormal springs 112 and 113 vand magnet 42 to battery. Lilie the 115 f connector, the selector releases upon the energization of the magnet 42, and opens the oli' normal spring contacts when the shaft reaches the lowest position. The relay 40, upon denergizing, alsoremoves the guarding ground from the banks of the individual vswitches and the holding ground from the relay 17, which falls back and again connects the relay 18 to thebattery. Thus the swlitclies are put in readiness for another. 125 ca l.

If 'the called line had been busy; when called from the substation A, the privateK `wiper 46 of. the-connector E' wouldA have found the conta-ct upon which it was rqtated 13g i arm 191,. contact point'196, springs 217 'and tion ofthe armature 1187fsimply causes the side switch'itolpass from firs Lto second position. The ymovement pf wipers 190 and 191 from fustto second position disconnects the ground Gr16 and the winding 188 fronrthe line conductors 15 and 16, and extendssaid conductors through -1 213 leading to a irst selector.

the conductors 92 and 98 and wipersv176 and 177- toa 'pair of' trunk conductors 212 and' The side switch arm 192, in its operated position, eX- tends a guarding ground potential over the conductor 211 to the connector prii'ate'bank contacts of the calling line. The side switch 'arm 193, in its operated position, extends a' guarding potential from ground G" through the contact point 208, arm 193,

lsprings 286 and 224, interrupter springs v221 and 222, brush 188 and wiper'179`to the `bank contact upon which it is resting, and

Atery. :This energizatlon of the winding 188 thence to the corresponding Contactin the ,banks of all the individual switches in the group. The side switch arm 194, in its opcrated position, connects the magnetl 210 with the shaft wiper 178, and hence with the release trunk (conductor 87 of the particular trunk line seized. The'calling subscriber may now extend his call through the selector and connector switches in the manner previously described. If the wipers of .the individual switch are standing on the contacts of a busy line when the receiver is removed from 'the switch hook, the wiper 179 is standing on vagrounded contact, -which ground 1s supplied through some other occupying switch in themanner eX- plained above.. I n this case `the attraction 'of the armature 187, upon the removal of the receiver, closes 'a circuit' from the grounded contact upon which the wiper 179 is-resting, through the brush 183, conductor 228, springs 222 and 221, 224"and .225 and winding 189 to battery B. The winding 189, upon energizing, attracts the armature '186,- which operates to rotate the shaft 175 one-step, to open the circuit of the winding 189 at the interrupter springs 221 and 222,

' and to close a circuit from ground G18 through the springs 226 and 227 and slow magnet 210 to battery. The magnet 210, upon energizing, operates to disconnect the ground G16 and winding 188 from the line vand to-prevent the side switch from passing to second position. By vproper adjustment oi the springs 224 and 22:3, and 226 and 227, the circuit of the magnet 210 may be closed before the side switch has left its normal position. When the circuit of the winding189 .is broken, the armature 186 e side switch tion as long yas the magnet 185 is operating to rotate the shaft. Soon after thearmature 1.86 has fallen back for the last time the magnet 210 denergizes and. again connects the winding 188 tothe line. `The armature'187 is thereupon attracted and trips the side switch inthe same manner as when the wipers are standing on the contacts of an idle trunk at the time the receiver is removed nfrom the hook. During the time the armature 186 is operating to rotate the wipers to an idle trunk line,.the winding 188 remains energized lover a circuit extending from the grounded bank contacts of the busy trunks through'the wiper 183, conductor 223, springs237 and 220and winding 188 tobatcauses the 'armature187 to hold the springs '224 Aand 225 in contact, so that the circuit vof the winding 189 ymay be4 closed each timev Ithe interruptersprings l221'and222 come into engagement as described. The energization of the winding 188 is not strong enough to interfere with the operation of the armature 186.

Vhen the calling subscriber hangs his receiver upon the completion ofthe conve'r- 4 sation, the selector and connector switches are released in themanner explained. SinceV the conductor 87 'is connectedto the spring 112 of the first selector, the magnet 210 of the individual switch will be energized in multiple withthe release; magnet 42 of the `first selector over a circuit extending-from ground to the spring 112, as previously traced, and thence-through the conductor 87 (Fig. l1), wiper 178, brush 182, contact arm.

194, contact point 204: and magnet 2 10 to` battery. The magnet210, upon energizing, forces ,the side switch of the individual switch-back .to its norma-l position, leaving the individual switch ready 'for use in another call. f

It will be seen lthat with vmy improved construction and lInode of operationv each -subscribers line switch is always in electrical connection with some one of the diiferent trunk lines leading therefrom. The connected trunk line, it will also `be seen, is always the vone last employed by the switch in extending-a call. For example, suppose that one of the switches is in electrical connection with a `trunk line over. which conversation is being carried on.,be'- tween the callingv and called-subscribers. In

such case the connected trunk line is, of course, the one last employed by the switch in extending the call.

is in electrical connection with one of the trunk lines, and the connected trunk line is thel one which .was last employed by the switch in extending a callingv connection. Invariably, therefore, as stated, each switch is normally and at all timesconnected with a trunk line which is the one last employed vby it in' extending a call. The switch thus controlled and operated is of such character that it always rotates in the same direction, and lhas no starting point ornormalposition, It simply remains each time inconnection with the trunk line thatwas employed in extending the call. It' in the in, tei-im that trunk line has been appropriated by some other subscriber, then when the iirst subscriber again calls, the switch will advance in a step-by-step manner to automatically select another trunk line. It is possible, however, in an exchange organized on the principle shown and described, for the subscribers to call many times without the necessity of. operating their line g switches in a step-by-step mannen' In any event, and when asubscriber calls, onlyone' line switch will ever operate, as inl order to find another idle trunk 1t 1s not necessary for the switch to 1n any way actuate he other switches of the same group.l Thus wear and tear is reduced toa minimum, and the certainty of operation is increased considerably, as .the .danger of a calling subscriber beginning to send in calling impulses before the line switch has found an idle trunk to a 'lirst selector is practically reduced to a minimum.

What I claim as my inventionis 1. In a telephone system, a line, a nonnuniierical trunking switch individual thereto, trunk lines for 'talking'purposes leading tl'icrefrom, said switch having'line v wipers always in electrical lengagement with some one 'of said trunk lines, which connected trunk line always the one last employed by said switch for extendinga call, normally open connections between said line and line wipers, a relay, inea-ns for energizing said relay over the line circuit, and means operated upon vthe energization of said relay to close said normally open connections.

2. In a telephone system, a line, a non numerical trunking switch, trunk lines-for talkingpurposes .leading therefrom, said switch having line wipersalways in electrical engagement with some one -of said trunk lines, which connected trunk line is always the one last employed by said switch for extending a call, said switch having a On the other hand,`

' assume that the same switch is at rest, and

that no talking circuit is being maintained thereby. Still, and in such case, the switch l 'wliic always the one step-by-step-actuatedshaft that always rotates in the same direction, normally open connections between ,said line :and line wipers, a relay, means for energizing said relay over the line circuit, and means operated upon the energi'zationof said relayr to closesaid normally open connections.

3, In va telephone system, a non-numerical trunking switch, Vtrunk lines for talking purposes leading therefrom, .said switch having line wipers always inelectrical engagementwithsome one of ysaid trunk lines, h connected trunk line is always the one last employed by said switch for extending a call, a telephone line to which said switch is individual, anda normally denergized relay controlling, ony energization, vthe connection between the said. tele-y phone line and switch.

L In a telephone system, an automatic trunking switch, trunk lines for talking purposes leading therefrom, terminals for said trunk lines, saidy switch having line wipers always in electrical engagement with the terminals of som'e one of said trunk lines, which connected trunk -line is y always the onelast employed by said switch .talking purposes leading therefrom, 'said switch having line wipers always in electrical engagement with some one of said trunk lines, which connected trunk line is last employed by 'said switch for extending a call, means for controlling 4said vswitch over the two sides of a metallic line. circuit in series, normallyI open connec` tions between said line andA line wipers, a relay, means for, energizing said relay over the line circuit, and means 'operated upon the energization of said relay lto* close said normally open connections.

' 6. In a'telephone system, a non-numerical trunking switch, trunk lines for talking purposes leading therefrom, said switch having line wipers always. in electrical engagement with some one of said trunk lines, which connected trunk line is always the one last employed by said switch for extending acall, an automatic selector switch at the other end of each of said trunk lines, and means for controlling` said switches over two sides oa metallii'line circuit-in series. 'f

7. Inv a telephone system, an automatic trunking switch, trunk lines vfor talkingpurposes leading therefrom, .terminals for iio izo

said trunk lines',l .said switch having line ywipers always in electrical 'engagement with the terminals of some one" of said trunk having line Wipers always in electrical engagement with some one of said trunk lines, which connected trunk line is always the one last employed by said' switch for extending a call, other switches for usingsaid trunk lines lin extending calls, .means allot-v ted to each trunk line for causing said firstmentloned switch to automatically select another trunk line. if the one which it used' last is bus y when it again responds to a call, norma y open connections between said' line and line wipers, a relay, means for energizing said .relay over they line circuit, and means operated upon the energization of said relay to close said normally open' connections.

9. In a* telephone system,l an automatic trunking switch, trunk .lines for talking purposes leading therefrom, terminals ,for said trunk lines, said switch having line wipers always in electrical engagement with the terminals vof some one of said trunk lines, which' connected trunkline is always the one last employed by said switch for extending a call, other switches for using said trunk lines in extending calls, means allotted to each trunk line for -causing'said first-mentionedv switch to automatically select another'trunk line if the one. which it used last is busy when it againfresponds to a call, normally open connections between said line and line wipers, a relay, means for energizing said relay over the line circuit, and means operatedupontheI energization of sald relay to .close said normally lopen connections.

copies ot this patent may 'te obtained for wipers contact with 10. In atelehone system, a line, a non numerical trun ing switch, trunk lines for talking purposes leading therefrom, said switch having -line wipers always in electrical 4connection withvone* of saidz'trunk lines, which connected trunk line is always the last one employed by said switch for extending a "call, normally-open connections between 'said line and'jline Wiper's, jand a' double-wound relay forl contr0lling,vupon energization, said ynormally open connections. p.

v11. In a telephone'system, a line, a non- 'numerical trunk'ing switch, trunk linesevfor ltalking purposes leading therefrom, said switch having line wipers always in electrical connection with ,one vof said trunk lines, whichconnected trunk line is always the last-oneA employed by said switch for extending acall, normally open connections between said'line and line wipers, a doublewou'nd relay for controlling said normally-` open connections, means for energizing said relay. to close said connections whenl connection is made with an idle trunk, and means for preventing said relay from ener-l gzing when said wipers contact with a busy-v trunk.

12.' -In a telephone system, a line, a non numerical trunking switch,.trunk lines for talking purposes leading therefrom, said switch 4having line wipers normally in elec-l trical engagement with one of said trunk lines, Vnormally open connections between said lineand line wipers, a relay lhaving a pair of windings, means for energizing one of Asaid windings to energize said relay to close said normally open' connections when connection' is'made with an idle ftrunk, and

'means to energize bothl of said windings to prevent said relay from operatin when said a busy trun Signed by me atl Chicago, Cook county,

Illinois, this thdayof J an1 1ary,', 191v1.

FRANKIJN J. 'raUBY. Witnesses :l

ARTHUR J. BAY, D. Farms.

ve cents each, by addressing the Commissioner o! Patents,

Washington, D. 0.

@@Wecionsn Lenersv Paent @a 3,1 22,556.,

Signed :1v/nd Seadd this 2nd .day of February, A, kf3., 1915.

i j lf'fshereby ue'tied that in Lamers Patent No. 1,122,556, granted December 29, G1914, upon the applicatio Q Fianklin Truby, of Chicago, Illinois, for an .y improvement in .Auton1.tiTrnking Systems, errors appear requiring correcftim as follows: Ip the drawings, SheQt-QKQFg. 2-thel'elays'f 52, in the Gon- Ictor E,shou1d be shown as dene/lg/eed instead of as now shwnin sai-d drawings;

page@ Of the px'inted specification, 1in@ thfoir the Word slefveuV Slide; and that y vthe Sad Letters Pafethouldbe read thse. corrections *therein that the; same mayA conform tio the lu'ecoc of thelcase in vthe Ptanic.'

{SEAL} j l R. E. WHTEHED,

Actin Chmwm'sszfone* 0 Patents.

ff"v 

